Wow... That's absolutely amazing.. The strokes for the painting seem big and vivid, but the texture that's being used for this gives a raw sort of feeling, and, in a way, seems to give moment of the ocean's water. Beautiful work!
My biggest difficulty is glare from relief brush texture. A scan gives me better resolution, but slightly skewed colors and glare has to be removed largely by hand, which can take several hours. When photographing my work I use polarized lighting gels and a polarized lens filter that remove all glare. By shooting in raw format and color correcting with a grey card I get the most accurate color I've managed. It's not as high resolution or crisp as a scan, but it's good enough for almost any application and it saves me those hours of glare removal.